Effect of cadmium on selected physiological and morphological parameters in metallicolous and non-metallicolous populations of Echium vulgare L.

• Metallicolous populations (M1, M2) accumulated more Cd than nonmetallicolous (NM).
• Cd tolerance decreased in the order M1>M2>NM.
• Malate and citrate might be involved in Cd detoxification in the roots of M1 and M2.
• PC production may be responsible for different Cd tolerances of NM and M populations.

Cadmium tolerance of three populations of Echium vulgare L., naturally occurring on two Zn–Pb waste deposits (metallicolous populations M1, M2) and on an uncontaminated site (non-metallicolous population, NM) was investigated. The plants were cultivated in hydroponics at 0, 5, 15, 30, or 50 μM Cd for 14 days. Although Cd reduced the content of photosynthetic pigments indifferently in the three populations, plant growth parameters and root viability analyses confirmed different Cd tolerances decreasing in the order M1>M2>NM in the populations studied. Organic acids (tartrate, malate, citrate, succinate) were not responsible for the elevated Cd tolerance of the metallicolous populations, although malate and citrate might participate in Cd detoxification in the roots of the M1 and M2. Phytochelatin concentrations were higher in the roots of M1 and M2 populations of E. vulgare, suggesting their role in Cd detoxification and different Cd tolerances.